The swine flu outbreak this spring is just the latest in the
mountain of ailments that seem to beset humanity, from the incurable
common cold to each potentially deadly cancer diagnosed at the rate of
every 30 seconds in the United States.

So is our species sicker than it has ever been? Or is our current lot far better than it used to be?

It turns out the answer to both questions might be yes. While humans
as a whole do live longer than ever before, we now suffer certain
illnesses to a degree never seen in the past — including skyrocketing
rates of diabetes and obesity and, surprisingly, ailments such as hay fever.

Among the possible causes for our modern ills: super-hygiene, sedentary lifestyles, and a lack of worms in our stomachs.

Life expectancy shot up dramatically
on average across the world during the 20th century, increasing from
just age 30 or so in 1900 to roughly age 67 now. (It’s not that many
people didn’t live to ripe old ages back then. Rather, the shift was
due in large part to vast reductions in the number of infant deaths,
which brought the average way down.)
In 1900, there was just one country worldwide where under one in ten
children died before their first birthday, while now out of the 187
nations for which there is data, this holds true for 168. These
striking changes are due in large part to improvements in nutrition,
sanitation and medicine.

"As a world population, on average we are far healthier than
before," said historian of medicine Naomi Rogers at Yale University.

Modern ailments

Infectious diseases once were the main cause of death worldwide,
"but around 1950 or so, there was a moment called the epidemiological
transition, a long term that just means that in most Western nations,
chronic diseases became the major causes of disability and death
instead," Rogers explained.

Although infectious diseases
seemed to Westerners to only be a "back then" or Third World problem
for decades, ever since HIV in the 1980s and 1990s, "I think that
element of hubris is gone," Rogers added. "But the infrastructure of
public health facilities that responded to infectious disease and
epidemics that disappeared in the United States has only slowly been
rebuilt, and there's now that shock that comes with new epidemics."

The modern era has brought a unique host of problems. The number of
American children with chronic illnesses has roughly quadrupled in the
past 50 years, including an almost fourfold increase in childhood obesity in the past three decades and twice the asthma rates since the 1980s.

"It's a combination of environment and lifestyle," Rogers said.
People are more sedentary and less physically active than before, and
fast food is more available.

"A powerful way of thinking of metabolic problems such as obesity
and diabetes regards toxic environments," she explained. "One study
showed that pregnant women living in areas that had large numbers of
fast food places gained very unhealthy levels of weight during
pregnancy compared with pregnant women who maybe lived a mile further
away. That's a toxic environment. So the society we live in has its own
dangers."

Body fights itself

Unusually, the number of ailments involving malfunctions of the immune system has gone up as well.

Multiple sclerosis, a disease where the fatty insulation around the
nervous system comes under attack, appears to be on the rise, and type
I diabetes, "a childhood form of diabetes almost unheard of at the turn
of the 20th century, is up from one in 5,000 or 10,000 to one in 250 in
some regions," said Joel Weinstock, chief of gastroenterology at Tufts
University Medical Center in Massachusetts.

Even hay fever, which plagues roughly 1 out of 4 people in the
United States, is something that may have largely emerged only in the
20th century, Weinstock said "What if I told you that there are some
countries that don't even know what hay fever is?" he asked.

The rise of these disorders might be due to the very improvements in
hygiene that have helped reduce infections in much of the world. The
body's immune system is regularly exposed to antigens, molecules that
it recognizes and reacts to, such as compounds from viruses or
bacteria.

"But the immune system needs to be controlled, needs to not act up
when exposed to things that aren't truly injuring you," Weinstock
explained. "What we think is happening is the regulation mechanisms are
becoming less effective. As to why that is, is it possible that it's
due to lack of exposure to antigens? Do you need to be exposed
regularly to antigens for it to work properly?"

You need worms

For instance, many fewer people are infected withworms than before.

"If you look back at the human race in the 20th century, every child
and adult had worms in their gastrointestinal tracts," Weinstock said.
"They were part of the ecosystem of the gut. As it turns out, worms are
very potent at controlling immune reactions, in order to live happily
ever after in the gut. Our theory is that when we started deworming the
population, that is one factor that led to the rise in immunological
diseases."

As part of this "hygiene hypothesis," Weinstock also notes that dirt
roads, horses and cattle used to be far more prevalent in life than
they are now.

"Our theory is that when we moved to this super-hygiene environment,
which only occurred in the last 50 to 100 years, this led to immune
disregulation," he said. "We're not saying that sanitation is not a
good thing — we don't want people to jog up to river banks and get
indiscriminately contaminated. But we might want to better understand
what factors in hygiene are healthy and what are probably detrimental,
to establish a new balance and hopefully have the best of both worlds."

Charles Q. Choi

Charles Q. Choi is a contributing writer for Live Science and Space.com. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.